Photovoltaic shingle system

ABSTRACT

A photovoltaic roofing shingle includes a strip of roofing material having an overlap portion, and a plurality of tab portions depending therefrom and separated by embossed inactive regions. Each of the tab portions includes a photovoltaic generating device affixed thereto. An encapsulating layer covers the top surface of each strip and wraps around the exposed and side edges. The photovoltaic devices are electrically interconnected, and each photovoltaic shingle member includes a hair of electrical terminals for delivering power from said photovoltaic devices. In use, the shingle members are affixed to a roof so that the tab portions of one row of shingles cover the overlap portion of an adjoining row. Electrical interconnection may be made through the roof to the inside of the building, or to a point atop the roof.

REFERENCE TO RELATED APPLICATION

This is a continuation-in-part of Ser. No. 175,968, filed Dec. 30,1993now U.S. Pat. No. 5,437,735.

FIELD OF THE INVENTION

The invention relates generally to photovoltaic devices and moreparticularly to a roofing material which is capable of generatingelectrical power. Most specifically, the invention relates to a roofingshingle structure which is compatible with conventional shingles andwhich is capable of generating electrical power.

BACKGROUND OF THE INVENTION

Photovoltaic energy is becoming a very significant source of electricalpower. This is because problems of scarcity and safety have limited theuse of fossil and nuclear fuels, and recent advances in photovoltaictechnology have made possible the large scale manufacture of low cost,light weight, thin film photovoltaic devices. It is now possible tomanufacture large scale, thin film silicon and/or germanium alloymaterials which manifest electrical and optical properties equivalent,and in many instances superior to, their single crystal counterparts.These alloys can be economically deposited at high speed over relativelylarge areas and in a variety of device configurations, and as such theyreadily lend themselves to the manufacture of low cost, large areaphotovoltaic devices. U.S. Pat. Nos. 4,226,898 and 4,217,364 bothdisclose particular thin film alloys having utility in the manufactureof photovoltaic devices of the type which may be employed in the presentinvention. However, it is to be understood that the present invention isnot limited to any particular class of photovoltaic materials and may bepracticed with a variety of semiconductor materials includingcrystalline, polycrystalline, microcrystalline, and non-crystallinematerials.

The power generated by a photovoltaic device is proportional to theillumination incident thereupon and if relatively large amounts of powerare to be generated, fairly large collection areas are required. Theroof and upper story areas of building structures are well illuminatedand are generally not put to productive use. For some time now it hasbeen known to place photothermal and photovoltaic collectors on the topportions of buildings. Roof mounted photovoltaic devices are shown forexample in U.S. Pat. Nos. 5,092,939; 5,232,518, and 4,189,881. Theseparticular photovoltaic roofing structures are of the batten and seamtype.

In many instances shingled roofs are favored, typically for residentialconstruction, and in those instances where fairly complex roofgeometries are encountered. In a typical shingle construction, roofingmaterial is supplied in rolls, or in precut pieces which aresubsequently laid in an overlapping configuration. In some instances,roofs are shingled with relatively thick tiles, which may be planar orof a curved cross-section. It will be appreciated that there is a needfor integrating photovoltaic power generation with shingled roofconstructions.

U.S. Pat. No. 4,040,867 describes a photovoltaic shingle constructioncomprised of a plurality of individual shingle members, each of whichhas a number of electrically interconnected single crystal photovoltaicdevices thereupon. In order to obtain high power from this type ofdevice, either the individual shingle must be made larger, or severalshingles need to be electrically interconnected. The first approachpresents problems of wind-loading; and the second approach results in aconstruction requiring a large number of weatherproof electricalinterconnections; also, leakage can result because of moisture creepbetween adjacent shingles by capillary action. Another configuration ofphotovoltaic shingle is described in U.S. Pat. No. 4,321,416. U.S. Pat.No. 3,769,091 depicts yet another photovoltaic roofing system comprisedof a number of individual silicon devices mounted in an overlappingrelationship.

The prior art has not been able to provide an acceptable shingle typephotovoltaic roofing system. Prior art devices are generally thick,inflexible, or of a geometry which makes them incompatible with standardconstruction techniques. As a result, prior art photovoltaic shinglestructures require specialized installation techniques and trainedpersonnel, which increases their cost and limits their utility.Furthermore, such structures cannot be easily integrated into aconventionally constructed roof. In addition, prior art photovoltaicroofing structures present aesthetic problems since the devices areoften of a distinctive color, or of a geometry such that they are veryobvious when installed.

Clearly, it would be desirable to have a photovoltaic roofing materialwhich is as much like conventional roofing material as possible. Thephotovoltaic portion of the roofing material should be self-contained toa large degree and be easily installed by conventional techniques. Itshould also be relatively lightweight, resistant to wind loading, andstable under harsh atmospheric conditions.

The present invention, as will be described in further detail hereinbelow, provides a roofing material which incorporates photovoltaictechnology into conventionally configured shingle stock. The roofingmaterial of the present invention is simple to install and efficientlyconverts light to electricity, and may be used in combination withstandard, non-photovoltaic shingle stock to cover any desired portion ofa roof. The particular configuration of the present invention makesefficient use of roof space for generating electricity and isunobtrusive in use. These and other advantages of the present inventionwill be readily apparent from the drawings, discussion and descriptionwhich follow.

BRIEF DESCRIPTION OF THE INVENTION

There is disclosed herein a photovoltaic roofing member which comprisesa strip of roofing material having a length "L_(s) " and a width"W_(s)." The strip includes an overlap portion having a length "L_(o) "which is equal to L_(s) and a width "W_(o)," which is less than W_(s).The strip also includes a plurality of tab portions depending from theoverlap portion. The tab portions are defined by at least one inactiveportion which may be formed by, alternatively, either a notch which iscut part way through the width of the strip or by an emboss molded intothe top surface of the strip. Each tab has a length "L_(t) " which isless than L_(s) and a width "W_(t) " which is less than W_(s), such thatW_(t) plus W_(o) equals W_(s). The roofing member further includes aplurality of photovoltaic devices, each affixed to a corresponding oneof said tabs. Each photovoltaic device includes a positive electrode, anegative electrode, and a body of photovoltaic material disposed therebetween. Each device is operative to generate a flow of electricalcurrent between the electrodes in response to the absorption of photonsby the body of photovoltaic material. The roofing member also includesan interconnect system for establishing electrical communication betweenthe plurality of photovoltaic devices, as well as a positive electricalterminal and a negative electrical terminal disposed in electricalcommunication with the interconnected devices. The terminals permitconnection of the photovoltaic roofing member to a load.

In particular embodiments, the strip of roofing material comprises amatrix of an organic, polymeric material having a body of fibrousmaterial therein. The polymeric matrix may comprise an asphalt basedmatrix and the fibers may comprise glass fibers. The tabs may includefurther elements such as stiffener elements fixed thereto and/or a bodyof sealant material. The front and/or back surface of the photovoltaicdevice may be encapsulated by a protective material, which, in onepreferred embodiment, extends around the exposed and side edges of thestrip. One particularly preferred type of photovoltaic device comprisesa flexible, thin film photovoltaic device such as a silicon-hydrogenalloy based device.

The interconnect system may comprise a set of jumper wires forestablishing a series, parallel, or mixed series/parallel electricalconnection between the photovoltaic devices. In one embodiment, theterminals are disposed on the back side of the roofing member so as topermit electrical current to be fed through, and to the bottom side of asupporting roof structure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a photovoltaic device of the typewhich may be employed in the practice of the present invention;

FIG. 2 is a top plan view of one embodiment of photovoltaic shinglestructured in accord with the principles of the present invention;

FIG. 3 is a cross-sectional view of the shingle of FIG. 2 taken alongline 3--3;

FIGS. 4A-C are rod plan views of other configurations of shinglesstructured in accord with the principles of the present invention:

FIG. 5 is a top plan view of a portion of a roof covered with thephotovoltaic shingles of the present invention;

FIG. 6 is a side elevational view of a house, having one end cut away,and including the photovoltaic shingles of the present invention;

FIG. 7 is a cross-sectional view of one photovoltaic shingle of thepresent invention shown affixed to a roof;

FIG. 8 is a top plan view of another embodiment of photovoitaic shinglestructured in accord with the principles of the present invention;

FIG. 9 is a perspective view of a portion of a roof covered with thephotovoltaic shingles of FIG. 8;

FIG. 10 is a cross-sectional view of the roof of FIG. 9 taken along line9--9;

FIG. 11 is an enlarged view of a portion of the shingle structure ofFIG. 8 illustrating the tapered notch thereof;

FIG. 12 is a top plan view of another embodiment of shingle structuredin accord with the principles of the present invention;

FIG. 13 is a perspective view of a portion of a roof covered with theshingles of FIG. 12;

FIG. 14 is a cross-section of the roof of FIG. 13 taken along line14--14; and

FIG. 15 is an enlarged view of a portion of the shingle of FIG. 12illustrating the tapered notch thereof;

FIG. 16 is a top plan view of yet another embodiment of a shinglestructured according to the principles of the present invention formedas an unnotched, embossed strip;

FIG. 17 is a cross-sectional view of the shingle of FIG. 16 taken alongline 17--17; and

FIG. 18 is a cross-sectional view of the shingle of FIG. 16 taken alonglines 18--18.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to a roofing shingle which generatesphotovoltaic power. It is to be understood that the present inventionmay be practiced in connection with a variety of differently comprisedand configured photovoltaic devices. Thin film photovoltaic devices arelow cost and light weight and can be fabricated upon flexible substratesand comprise one particularly preferred group of devices which may beused in the practice of the present invention. One particularlypreferred group of thin film photovoltaic devices comprises thosefabricated from alloys of group IVa semiconductor materials,particularly silicon-hydrogen and germanium-hydrogen alloys; although,it is to be understood that the present invention may also be practicedin connection with otter thin film materials such as CdS, CuInSe₂ andGaAs as well as single crystalline, polycrystalline, andmicrocrystalline photovoltaic materials.

Referring now to FIG. 1, there is shown, in cross-section, oneparticularly preferred photovoltaic device 10, which may be employed inthe practice of the present invention. The device 10 of FIG. 1 is atandem NIP type photovoltaic device made up of a plurality of individualn-i-p type cells 12a, 12b, and 12c disposed in an optical and electricalseries relationship between a substrate electrode 11 and a ton electrode22. The substrate 11 is preferably formed from a thin, electricallyconductive material such as a layer of stainless steel, aluminum, or thelike. In some instances, the substrate 11 may comprise a body ofinsulating material such as glass, or a polymeric material, having anelectrically conductive layer deposited thereupon. In some instances,the substrate 11 includes a back reflector deposited thereupon. The backreflector may be a single or multiple layered structure which has a topsurface that is smooth or textured, and serves to increase theefficiency of the device by reflecting unabsorbed light back through theoverlying semiconductor layers. It is to be understood that within thecontext of this disclosure, the terms substrate, or substrate electrodeshall refer to any assemblage of layers which support the remainingportion of the photovoltaic device and provide a bottom electrodethereof.

Each of the cells 12a, 12b and 12c includes at least one layer of ahydrogenated group IVa semiconductor material. As illustrated, each ofthe cells 12a, 12b, and 12c includes a layer of p type semiconductormaterial 20 and a layer of n type semiconductor material 16, with alayer of substantially intrinsic semiconductor material 18 interposedtherebetween. In some instances, the intrinsic layer 18 may be ofslightly p or n type conductivity; however, with regard to the dopedlayers, it is essentially electrically neutral, and is referred toherein as being a substantially intrinsic layer. In the illustratedembodiment, the structure includes three stacked cells 12a, 12b, and12c. It is to be understood that a greater or lesser number of cells maybe similarly disposed.

Atop the uppermost cell 12c is a top electrode 22. This electrode isfabricated from a transparent, electrically conductive material,typically a transparent conductive oxide (TCO) such as tin oxide, indiumoxide, indium tin oxide, zinc oxide cadmium stannate, or combinationsthereof. Generally, an electrode grid 24 is disposed atop the TCO layer22 to enhance the collection efficiency of photogenerated current. Insome embodiments, the intrinsic layers 18 of each of the cells 12a, 12b,12c are formed from semiconductor alloy materials having different bandgaps, so as to make maximum use of incident illumination. For example,the intrinsic layer 18 of cell 12c may have a band gap of approximately1.7 eV; the intrinsic layer 18 of cell 12b may have a band gap ofapproximately 1.5 eV, and the intrinsic layer 18 of cell 12a may have aband gap of approximately 1.3 eV. Such tandem devices, and methods fortheir fabrication are well known in the art.

Referring now to FIG. 2, there is shown a top plan view of aphotovoltaic roofing member 26 configured as a strip of shingle materialin accord with the principles of the present invention. The roofingmember 26 comprises a string of roofing material 28 of a generallyrectangular, elongated shape having a length L_(s) which is greater thanits width W_(s). The strip of roofing material 28 is configured todefine a plurality of portions. The first portion is a generallyrectangular overlap portion 30 which has a length Lo coextensive withthe length L_(s) of the strip 28, and a width W_(o) which is less thanthe width W_(s) of the strip 28. Depending from the overlap portion 30are a number of separate tab portions 32. The tab portions are definedbv one or more notches 34 which are cut part way through the width W_(s)of the strip 28. The tabs each have a length L_(t) which is less thanthe length L_(s) of the strip and a width W_(t) which is less than thewidth W_(s) of the strip. The width of the tabs and the width of theoverlap portion are such that W_(o) plus W_(t) equals W_(s). It ,sill benoted that in the illustrated embodiment, the notches 34 do not extendthe full width W_(t) of the tabs; however, in accord with the presentinvention, the notches 34 may be made longer or shorter. Also, the tabs32 are shown as being rectangular; it is to be understood that aestheticconsiderations may dictate that the free ends thereof be configured inanother shape such as a different polygonal shape or a curved shape.

Disposed upon a ton surface of each tab portion 32 is a photovoltaicdevice 36. As discussed hereinabove, the devices 36 may be of variousmaterials and configurations, and in one preferred embodiment they arethin film devices fabricated from group IVa semiconductor alloys. Eachof the photovoltaic devices 36 includes a top and a bottom electrode asdiscussed above, and is operative to absorb incident illumination andprovide a flow of current between said electrodes in response thereto.

The photovoltaic roofing member 26 of FIG. 2 further includes aninterconnect system for establishing electrical communication betweenthe photovoltaic devices 36. As illustrated, this interconnect systemincludes a number of jumpers 38 joining the devices 36. The jumpers 38may comprise cables, wires or tapes fabricated from copper or some othersuch material with good electrical conductivity. As is well known in theart, the devices 36 may be interconnected in a series configuration, aparallel configuration or a mixed series-parallel configuration. Byappropriately configuring the interconnections, current and voltage ofthe resultant combination may be controlled. In some instances, it maybe desirable to dispose the jumpers 38 comprising the interconnectsystem so that they extend further into the overlap portion 30 of thestrip 28, so that they will be covered by adjoining shingles when inuse. In other instances, interconnection may be accomplished from therear surface of the roofing member 26. The roofing member 26 alsoincludes a positive and a negative electrical terminal for withdrawal ofpower therefrom. The terminals are in electrical communication with theinterconnected plurality of photovoltaic devices.

Referring now to FIG. 3, there is shown a cross-sectional view of theroofing member 26 of FIG. 2 taken along line 3--3. Visible in the figureis the strip of roofing material 28 showing the overlap portion 30 andtab portion 32, together with the photovoltaic device 36 as disposedupon the tab portion 32. In the illustrated embodiment, the photovoltaicdevice includes a top layer of protective material 40 disposedthereupon. This protective layer 40 is shown as extending across theentire ton (i.e., light incident) surface of the photovoltaic device 36and onto the overlap portion 30 of the strip 28 of roofing material. Theprotective layer 40 is optional, and serves to protect the photovoltaicdevice 36 from ambient atmospheric conditions. The protective layer 40is preferably an inert, optically transparent material. Fluoropolymerscomprise one preferred group of protective materials, and a materialsold by the Du Pont Corporation under the tradename Tefzei has beenfound to be advantageous. The protective layer is typically adhered tothe photovoltaic device with a bondable material such as an ethylenevinyl acetate (EVA). In the illustrated embodiment, the top protectivelayer 40 covers the photovoltaic device 36 and the remainder of the tab32 as well as all of the overlap portion 30. In some embodiments, a topprotective layer may cover only the photovoltaic device, or it may coverthe device and only a portion of the strip 28. In the illustratedembodiment, a bottom protective layer 42 is also included. This layer isgenerally similar to the top protective layer; however, opticaltransparency is not necessary; and hence, opaque materials may beemployed. Typically, the bottom protective layer, utilized, comprises apolymeric material. The strip 28 is preferably fabricated from standardroofing stock, and as such comprises a fibrous material such as glassfiber, ceramic fiber, vegetable fiber, or synthetic polymeric fiberdisposed in a moisture resistant matrix. The matrix typically comprisesan organic polymeric material of natural origin such as asphalt, pitch,rubber, or the like, or it may comprise a synthetic polyrneric material.In some instances, the strip 28 of roofing material may comprise amultilayered composite. In other instances, the strip may comprise astrip of polymeric materials. In general, any roofing material known inthe art may be adapted for use in the present invention.

The roofing member may optionally include a stiffening member 43disposed along the free edge of the tab portion .32. The stiffeningmember 43 is formed from a rigid material, such as a metal or polymericstrip, and it serves to prevent excessive longitudinal flexing of thetab 32. The roofing member 26 may also include a body of sealant 45 onthe bottom side of the tab 32. The sealant is typically a thermoplastic,contact. adhesive material such as a tar, asphalt, or synthetic polymerbased material, and it serves to adhere the tab 32 to an underlyingshingle. As is known in the art, the body of sealant 45 may be protectedby a strip of release paper or the like.

Depending upon the particular application, the roofing member of thepresent invention may be manufactured in a variety of configurations.Referring now to FIGS. 4A-4C, there are shown some such variations. FIG.4A shows a roofing member 44 including three tabs 32 of approximatelyequal lengths. FIG. 4B shows a roofing member 46 which includes only twotabs 32 and 33 defined bv a single notch 34. It should be noted that tab33 is of a smaller length than tab 32, and includes a correspondinglysmaller photovoltaic device 35 thereupon. FIG. 4C shows yet anotherconfiguration of roofing member 48 which includes three tabs. Two of thetabs 32 are of approximately equal length and the third tab 33 is asmaller tab. In FIG. 4C, the small tab is on the right side of theroofing member 48, and in the FIG. 4B embodiment, the small tab is onthe left side thereof. It will be appreciated that through the use ofthe variously configured members illustrated herein, differing areas andshapes of roofs may be effectively covered.

The roofing members of the present invention are installed in the mannerof conventional strip shingle material; that is to say, a first row ofmembers is attached to a roof by nailing through the overlap portionthereof. A second row is affixed in place so that the tab portionsthereof overlap, and cover the majority of the overlap portion of thefirst row. Succeeding rows are laid in the same manner. By the use ofappropriately shaped pieces at the ends thereof, a uniform area may beeffectively covered.

Referring now to FIG. 5, there is shown a portion 47 of a roof havingthree rows, 49a, 49b, and 49c, of shingle material of the presentinvention installed thereupon. It will be noted that the appearance iscomparable to that of a standard shingled roof and the presence of thephotovoltaic device, and any optional encapsulant layer, furtherenhances the durability of the shingles. It has been found that byappropriately control of the thickness, and in some instances thestoichiometry, of the TCO layer of the photovoltaic device, theperceived color of the device may be controlled so as to match theremainder of the roof. Because of the fact that the shingles of thepresent invention are similar in appearance and method of installation,to conventional shingle material, they may be inconspicuously integratedinto conventionally constructed roofs without the need for anyspecialized tools or labor.

Referring now to FIG. 6, there is shown a side elevational view of abuilding having a portion of the roof 50 thereof covered with a numberof strips of photovoltaic shingles 26 of the present invention. FIG. 6illustrates the manner in which the photovoltaic shingles are affixed inan overlapping relationship. It will also be noted that the figure showsa number of electrical terminal pairs 52 projecting through the roof 50to the interior of the building. Each of these terminal pairs 52 is inelectrical communication with the interconnected photovoltaic devices ofeach strip 26 and thereby provides a positive, and a negative electricalterminal for withdrawal of power therefrom. The individual terminalpairs 52 may be electrically interconnected to a load or power storagesystem.

Referring now to FIG. 7, there is shown a sectional view of a portion ofthe roof 50 showing one photovoltaic shingle member 26 affixed thereto.It will be seen that the terminal pair passes through the roof 50 from ajunction box 54 on the rear surface of the shingle member 26. In keepingwith the present invention, a body of caulking or sealing material maybe further included with the junction box 54 to seal the opening throughthe roof. In another embodiment, the electrical leads coming out of thestrip of roofing material 26 can be a pair of electrically insulatedwires. The insulation extends to the photovoltaic devices and iscompletely covered by the rear surface laminate. The junction box iseliminated, and the material presents a flat rear surface. Since thejunction box is eliminated, the wires may be passed through the roofthrough a relatively small sized hole, having a diameter comparable tothat of a nail hole used to fasten the shingle to the roof. Thisapproach can eliminate the need for caulking material. In someinstances, it may not be possible, or desirable to bring electricalconnections in through the roof, and such instances, the terminals maybe otherwise placed on the shingle, as for example on the front surface,or at the edge.

The foregoing embodiments were directed to shingle structures forproviding a relatively planar roof surface. In some instances, tiledroof structures are employed, and these tiles frequently have curvedcross sections. Accordingly, it is desirable to have a photovoltaicroofing material which is compatible with curved tile roofs. In accordwith another embodiment of the present invention, there is provided ashingle structure which may be integrated with variously curved roofingtiles.

Referring now to FIG. 8, there is shown a portion of a photovoltaicroofing member 60 which is configured to be employed in combination withcurved roofing tiles. The member 60 is generally similar to the memberspreviously described, and includes an overlap portion 30 and a pluralityof separate tab portions 32, each of which has a photovoltaic device 36disposed thereupon. As in the previous embodiments, each tab 32 isdefined by at least one notch 62.

As is best shown in FIG. 11, each notch 62 of the FIG. 8 embodiment, isa tapered notch, and within the context of this disclosure, a taperednotch is defined as a notch having two nonparallel sides defining thelength thereof. As such, it is to be contrasted to a straight, orparallel notch, in which the two sides defining the length are parallel.It is to be noted that the notch in FIG. 11 is tapered so that the width"W_(n) " thereof varies and is greatest proximate the root end 64 of thenotch 62, and is smallest proximate the free end 66 of the notch 62.

The tapered notches 62 permit the tabs 32 of the shingle structure 60 ofFIG. 8 to be curved when the shingles are installed on a roof so thatthe resultant structure is simulative of, and compatible with, roofsmade of curved tiles.

Referring now to FIG. 9, there is shown a portion of a roof covered withthe shingles of FIG. 8. Illustrated therein are three strips 60a, 60b,60c and it will be noted that the tab portions 32 thereof are curved inthis installation, although the overlap portion, 30 of 60a remains flat,and provides a base for the tab portions of adjacent shingles, forexample, 60b. In installations of this type, the shingles are installedso that the tabs on adjacent strips are aligned. It will be noted thatthe curvature of the tabs varies, and is greatest proximate the free endthereof, and decreases as the tab approaches the overlap portion 30.FIG. 10 is a cross-sectional view of the roofing structure of FIG. 9taken along line 9--9 showing four tabs 32c of the shingle 60c, andillustrating the curvature thereof.

Other configurations of shingle for use in combination with curved tileroofs are possible in accord with the present invention. In someinstances, roofs are fabricated from alternating rows of curved and flattiles, and FIG. 12 illustrates yet another shingle structure 70 inaccord with the present invention. The shingle 70 of FIG. 12 includes anoverlap portion 30 and a plurality of tabs 32, with photovoltaic devices36 attached thereto, as previously described. The tabs are defined by aplurality of notches 72, which in this embodiment are tapered notches ofa particular configuration.

Referring now to FIG. 15, there is shown an enlarged view of a portionof the shingle 70 of FIG. 12, better illustrating the tapered notch 72thereof. The notch 72 is tapered, as previously described and as suchincludes two non-parallel sides along the length thereof and the taperis disposed so that width of the notch is greatest proximate the routeend 64 thereof. It will be noted from the figure that the notch 72 isconfigured so that one of the sides 74 thereof forms a corner 76 withthe free edge 78 of the tab 32, which corner is a right angled corner. Asecond edge 80 forms a corner 82 with a free edge 78 of an adjoiningtab, which corner 82 is an acutely angled corner.

Referring back to FIG. 12, it will be noted that the notches 72 may beconfigured so that alternating tabs are bounded by right angled corners76 and acutely angled corners 82, respectively. The tabs having rightangled corners, for example tabs 36-x, will lie flat when the shingle 70is installed and those tabs, for example tabs 36-y with acutely angledcorners, will curve.

Referring now to FIG. 13, there is shown a perspective view of a portionof a roof installation employing the shingles 70 of the presentinvention. It should be noted that the particular configuration of thenotches provides for alternating flat and curved rows.

FIG. 14 is a cross-sectional view taken along line 14--14 andillustrating the curved, 36-y and flat, 36-x tabs. In keeping with thesegeneral principles, various other configurations of flat and curvedshingle structures may be prepared.

In instances where roofs are configured to include dormers and othersuch structures, the intersection between the dormer and the gable willform a compound angle. Mounting of the roofing material of the presentinvention may be accomplished by either preconfiguring one of the edgesof the roofing material so that the photovoltaic cell on the tab portionthereof is cut at an angle which will permit the strip to be fitted tothe dormer. In other instances, the end tab of the strip is free ofactive photovoltaic material, and as such may be custom cut in the fieldto hermit fitting of the roof material to permit flush mounting alongthe intersection line.

Referring now to FIGS. 16-18, there is shown an alternate embodiment 80of the roofing member of the present invention. In FIG. 16, which is atop plan view of the roofing member 18, a plurality of photovoltaicdevices 82 are arrayed along the length of the roofing member 80, in alinear, spaced-apart relationship. Interposed between adjacent pairs ofphotovoltaic devices 82 are inactive regions 84. However, instead ofbeing formed of cut-out notches, as is the case of the embodimentsdepicted in FIGS. 1-15, the inactive regions 84 are formed of embosseswhich are simply molded into encapsulant layer 88. Preferably,encapsulant layer 88 is formed of an inert, optically transparentmaterial, such as the Tefzel fluoropolymer, bonded to the device asdiscussed earlier. Since the Tefzel protective layer 88 is opticallytransparent, the underlying material is visible therethrough. Thus, theinactive regions 84, on which no semiconductor material is disposed,will show the underlying material of the member 80. Optionally, a layerof colored or textured material may be disposed on the inactive regions84 for a more cosmetic appearance. Embossing the encapsulant layer 88 sothat the embossing overlies the inactive regions 84 creates theappearance that photovoltaic devices 82 are separated. In this manner,the appearance of conventional roofing shingles is mimicked.

Preferably, (as is best seen in FIGS. 17 and 18), the encapsulant layer88 overlies both the plurality of photovoltaic devices 82, as well asthe inactive regions 84, and extends for a short distance onto overlapportion 86 of the roofing member 80. In this embodiment, the encapsulantlayer 88 wraps around exposed edge 90, as well as side edges 92 of themember 80 and for a short distance onto bottom surface 94 of member 80.In this way, all of the exposed areas of member 80 are protected byencapsulant layer 88.

The embodiment illustrated in FIGS. 16-18 has certain advantages overthe other illustrated embodiments. For example, it should be noted thatthe encapsulant layer 88 is continuous along the length of the member80. Since the encapsulant layer 88 wraps around the exposed and sideedges 90, 92 of the member 80, all of the layer edges are protected fromexposure, thereby preventing moisture from creeping between thephotovoltaic device and encapsulant layer. Furthermore, since actualnotches are not cut into the member 80, the photovoltaic devices 82, canbe located closer to the edges 90, 92 of the member 80. Additionally,the plurality of photovoltaic devices 82 may be spaced more closely toeach other; that is, the photovoltaic devices can be located very closeto the inactive region of the emboss. The resultant increase in thepercentage of the roofing member covered with photovoltaic devices canbe readily seen by comparing FIG. 16 with FIG 1. Since a greaterpercentage of the surface area of the roofing member is photovoltaicallyactive, the member is more efficient; it is estimated that, in a roofingmember such as that illustrated in FIG. 16, approximately 93-94% of theexposed area of the member 80 is photovoltaically active.

Furthermore, by eliminating the notches in the roofing member, themember is more stable and reliable. It is also easier to install. Thus,the embodiment of the present invention shown in FIGS. 16-18successfully simulates conventional asphalt shingle roofing in itscosmetic appearance, and also is more energy efficient, easier tomanufacture and install, and more stable and reliable.

It will thus be appreciated that the shingle construction of the presentinvention provides for roof top mounted. photovoltaic generating unitswhich are inconspicuous, light in weight and easy to install. Because ofits particular configuration, the photovoltaic material, in addition toproviding electrical generating capacity, provides a durable highquality roof. The combination of overlap and tab portions allows forready integration with conventional roofing systems and provides aweather tight, wind resistant construction. The presence of thephotovoltaic devices actually enhances the strength and durability ofthe roofing material.

While the foregoing invention was primarily described with reference toparticular embodiments, it will be understood that numerous othervariations will be readily apparent to one of skill in the art from thedrawings, discussion and description of the particular embodimentspresented herein. Therefore, it is the following claims, including allequivalents, which define the scope of the invention.

We claim:
 1. A photovoltaic roofing member comprising:a strip of roofingmaterial having a length "L_(s) " and a width "W_(s)," said stripincluding an overlap portion having a width "W_(o)," which is less thanW_(s), said strip further including an exposed portion having a width"W_(t) " which is less than W_(s), such that W_(t) plus W_(o) equalsW_(s) ; a plurality of photovoltaic devices linearly arrayed in aspaced-apart relationship along the length of the said exposed portion,and each including a positive electrode, a negative electrode, and abody of photovoltaic material disposed there between, each deviceoperative to generate a flow of electrical current between saidelectrodes in response to the absorption of photons by said body ofphotovoltaic material; an interconnect system for establishingelectrical communication between said plurality of photovoltaic devices;a positive electrical terminal and a negative electrical terminaldisposed on a bottom surface of said roofing member and in electricalcommunication with the plurality of photovoltaic devices; an inactiveregion interposed between each adjoining pair of said plurality ofphotovoltaic devices; and an encapsulant layer of transparent,nonconductive material disposed on said exposed portion so as to overliesaid photovoltaic devices and said inactive regions, said encapsulantlayer being embossed in portions thereof overlying said inactive regionssuch that said strip of roofing material is visible through saidencapsulant layer.
 2. A roofing member as in claim 1, whereinencapsulant layer is formed of a fluoropolymer.
 3. A roofing member asin claim 1, wherein said plurality of photovoltaic devices comprises aplurality of flexible, thin film, photovoltaic devices.
 4. A roofingmember as in claim 1, wherein said body of photovoltaic materialincludes at least one layer of a silicon-hydrogen alloy material.
 5. Aroofing member as in claim 1, wherein said body of photovoltaic materialincludes at least one triad comprised of a layer of substantiallyintrinsic semiconductor material interposed between oppositely dopedlayers of semiconductor material.
 6. A roofing member as in claim 1,wherein said interconnect system includes a plurality of electricallyconductive jumper wires for establishing electrical communicationbetween said plurality of photovoltaic devices.
 7. A roofing member asin claim 1, wherein said interconnect system is operative to establish aseries electrical connection between said plurality of photovoltaicdevices.
 8. A roofing member as in claim 1, wherein said interconnectsystem is operative to establish a parallel electrical connectionbetween said plurality of photovoltaic devices.
 9. A roofing member asin claim 1, wherein said interconnect system is operative to establish amixed series-parallel interconnection between said photovoltaic devices.10. A roofing member as in claim 1, wherein said strip of roofingmaterial has two opposed side edges and an exposed bottom edge, saidencapsulant layer extending around said bottom and side edges.
 11. Aroofing member as in claim 10 wherein said encapsulant layer furtherextends partially onto the bottom surface of said roofing member.
 12. Aroofing member as in claim 1 wherein said encansulant layer furtherextends partially onto said overlap portion.
 13. A photovoltaic roofingmember comprising:a strip of roofing material having a length "L_(s) "and a width "W_(s)," said strip including an overlap portion having alength "L_(o) " which is equal to L_(s) and a width "W_(o)," which isless than W_(s), said strip including a plurality of tab portionsdepending from the overlap portion, said tab portions being defined by aplurality of inactive regions interposed between said tab portions; eachtab having a length "L_(t) " which is less than L_(s) and a width "W_(t)" which is less than W_(s), such that W_(t) plus W_(o) equals W_(s) ; aplurality of photovoltaic devices, each affixed to a corresponding oneof said tabs and each including a positive electrode, a negativeelectrode, and a body of photovoltaic material disposed there between,each device operative to generate a flow of electrical current betweensaid electrodes in response to the absorption of photons by said body ofphotovoltaic material; an interconnect system for establishingelectrical communication between said plurality of photovoltaic devices;and a positive electrical terminal and a negative electrical terminaldisposed on a bottom surface of said roofing member and in electricalcommunication with the plurality of photovoltaic devices.
 14. A roofingmember as in claim 13 wherein each of said plurality of inactive regionsis defined by a notch cut part way through the width of the strip, saidnotch having a length which is less than Wt.
 15. A roofing member as inclaim 13 wherein said member further includes an encapsulant layer oftransparent, nonconductive material disposed on said exposed portion soas to overlie said photovoltaic devices and said inactive regions, eachof said plurality of inactive regions being covered by an emboss formedin said encansulant layer and overlying said inactive region such thatsaid strip is visible through said emboss.
 16. A roofing member as inclaim 15, wherein said strip of roofing material has two opposed sideedges and an exposed bottom edge, said encapsulant layer extendingaround said bottom and side edges.
 17. A roofing member as in claim 15wherein said encapsulant layer further extends partially onto the bottomsurface of said roofing member.
 18. A roofing member as in claim 15wherein said encansulant layer further extends partially onto saidoverlap region.